1. Field of the Invention
The present invention relates to an electronic weighing apparatus. More specifically, the present invention relates to an apparatus that is adapted for displaying in a digital manner the measured weight of an article and a price of the article evaluated on the basis of the measured weight and a unit price preset in advance.
2. Description of the Prior Art
A conventional electronic weighing apparatus which has been put in practical use has been adapted to measure the weight of an article, evaluate the price of the article based on the measured weight and a unit price thereof set in advance, and to display such data in a digital manner, thereby to provide both the seller and the purchaser with simplicity and accuracy of viewing the display, whereby the weighing is facilitated and trust is placed in each other. Typically, such an electronic weighing apparatus comprises a scale mechanism comprising a displacement member responsive to the weight of an article being weighed for causing displacement associated with the weight of the article, a pulse generator responsive to the displacement of the displacement member for providing a pulse train a number of pulses associated with the displacement of the displacement member and thus representing the weight of the article, each pulse representing a predetermined weight, say 2 g, a counter for counting the number of pulses for evaluating the weight of the article, and a display for displaying the measured weight in a digital manner.
In measuring the weight of an article with such an electronic weighing apparatus as described above, it may happen that the weighing plate of the scale mechanism moves up and down repeatedly in an attenuated manner. As a result, the display of the weight and thus the price is observed as repetitive changes of the indicated numerals and thus looks flickering. Such flickering of the display in an electronic weighing apparatus for displaying the data in a digital manner could also be caused by the following reasons. An inherent mechanical vibration of the scale mechanism, caused by a motor installed in a show case, for example, may cause minor variations in the displacement, which in turn results in flickering of the display. Wind could also cause a small movement of the weighing plate, which again causes flickering of the display. The fact that the repetitive changes of the displayed weight value and the price or the flickering of display occurring by the above described internal and external causes, however, requires time for stabilized measurement and makes perchasers feel distrustful of the displayed data.
Various countermeasures for preventing repetitive minor changes of the displayed data or flickering of the display as described above have also been proposed. One approach is to measure time by means of clock pulses to load a new data such as a weight value at every sampling time of say 100 ms in a given time period commensurate with, for example, one operation cycle of say 0.5 second, whereby the displayed data is adapted to be kept unchanged for the above described period of 0.5 second. Another approach comprises a particular step for reading the data in a display register during a time period corresponding to, for example, an operation cycle, as programmed, whereby a new weight value is sampled and displayed for each step, with the result that the same effect is attained. A further approach is to provide an amplifying circuit with a low pass filter of a large time constant, whereby transition in displacement, i.e. transition in an electrical signal change may be eliminated. Any one of the foregoing approaches, however, has the disadvantage that a response time is prolonged. In particular, the last mentioned approach is disadvantageous in that the sensitivity of the measurement per se is reduced.